A photographic material is generally produced by coating one or more photographic layer (light-sensitive layer) on a plastic film support. As the plastic film support, celluloses such as triacetyl cellulose (hereinafter referred to as "TAC") or polyesters such as polyethylene terephthalate (hereinafter referred to as "PET") generally are employed.
A photographic material is generally classified into two groups: a film in the form of a sheet such as an X-ray film, a film for photomechanical process or a cut film; and a film in the form of a roll such as a color or black-and-white film having a width of 35 mm or less which is incorporated into a cylindrical cartridge (patrone). The latter film is usually employed by charging in a camera for shooting.
As material of a support for a roll film, TAC is mainly employed. The TAC has the features of a high transparency and no optical anisotropy, and further has a property of easily smoothing the curl of the film caused after development (easily curl-smoothing property).
In contrast, when a photographic material having a support which has not such an easily curl-smoothing property (that the TAC has) is used in the form of roll, scratching and out-of-focusing occur during the printing step of forming an image on a photographic printing paper, or jamming occurs during feeding of the film in the printing step.
The photographic materials has been developed to a variety of uses in these days. For instance, increase of a feeding speed of a photographic film in a camera per each shooting, increase of the image magnification and reduction of the size of the camera have been desired. The desired characteristics can be obtained by use of a support having a high bending strength, a good dimensional stability and a reduced thickness.
Particularly, the reduction of the size of the camera or the patrone is desired. To satisfy the desire, a diameter of a spool around a film is wound up is required to be reduced.
There are two problems to be solved in order to attain the size-reduction of the patrone:
One of the problems resides in the reduction of the modulus of elasticity in bending (concerned with brittleness) with reducing the thickness of the film. PA1 The second problem resides in a strong curl tendency developed with elapse of time due to the reduction of the size of the spool (of the cartridge). PA1 1) The silver halide photographic material wherein the breaking elongation is in the range of 80 to 200% (preferably 90 to 200%). PA1 2) The silver halide photographic material wherein the support has surface roughness of 0.0015 to 0.050 .mu.m (preferably 0.002 to 0.050 .mu.m). PA1 3) The silver halide photographic material wherein the support further contains a fine particle having a particle size of 0.03 to 2.5 .mu.m in the amount of 0.001 to 0.8 weight %. PA1 4) The silver halide photographic material as above 3) wherein the fine particle is a spherical particle of silica, silicone or crosslinked polystyrene. PA1 5) The silver halide photographic material wherein at least one surface of the support is subjected to a corona discharge treatment, a glow discharge treatment or a UV treatment (preferably a glow discharge treatment). PA1 6) The silver halide photographic material which is wound around the spool having the diameter of 3 to 12 mm. PA1 7) The silver halide photographic material wherein the support has a thickness of 50 to 100 .mu.m. PA1 8) The silver halide photographic material wherein the support has been biaxially stretched in the condition of the stretching magnification of 2.8 to 3.8 in both lengthwise direction and widthwise direction. PA1 9) The silver halide photographic material as above 8), wherein the support has been subjected to heat setting at 190.degree. to 260.degree. C. for 1 to 60 second after the biaxial stretching. PA1 10) The silver halide photographic material as above 8), wherein the support subjected to the biaxial stretching has been further subjected to heat treatment at a temperature of 50.degree. C. to the glass transition temperature for 0.1 to 1,500 hours before forming the silver halide emulsion layer on the support. PA1 11) The silver halide photographic material wherein the support has haze of not more than 3%. PA1 12) The silver halide photographic material wherein the support has friction coefficient between two supports of not less than 0.6. PA1 13) The silver halide photographic material wherein the support has thermal shrinkage factor of not more than 0.3% after allowing it to stand at 110.degree. C. for 30 minutes. PA1 14) The silver halide photographic material as above 3) wherein the support further contains a deposited particle produced during preparation of polyester. PA1 15) The silver halide photographic material wherein the support has intrinsic viscosity of not lower than 0.45 based on a viscosity measured in orthocresol at 35.degree. C. PA1 16) The silver halide photographic material which is a film in the form of a roll.
However, the TAC film has a stiff molecular structure and therefore the obtained film is too brittleness to reduce the thickness.
U.S. Pat. No. 4,141,735 discloses a process for reducing core-set curling tendency and core-set curl of polymeric film elements (polyester such as PET) which comprises heating a sheet or roll of self-supporting, core-set-prone thermoplastic polymeric film, at a temperature in the temperature range of from about 30.degree. C. up to about The glass transition temperature (Tg) of said polymer for 0.1 to 1500 hours. The PET film is extruded at 200.degree. C. or higher to be subjected to a heat treatment. In such heat treatment, the heated film usually is first stretched lengthwise 2 to 3 times its original length, and then similarly stretched widthwise. The finished film is further subjected to the above-described heat treatment to reduce core-set curling tendency.
However, the silver halide photographic film using the film subjected to the heat treatment in the patent is not sufficiently improved in the curling tendency and reduction of strength.
As examples of a film for the silver halide photographic film, biaxially stretched films of poly(ethylene-2,6-naphthalate), which has a high strength, have been proposed (Japanese Patent Publication No. 48(1973)-40414; and Japanese Patent Provisional Publications No. 50(1975)-81325 and No. 50(1795)-109715). Japanese Patent Provisional Publications No. 50(1795)-109715 describes a film of poly(ethylene-2,6-naphthalate) for a photographic material having a high Young's modulus (not less than 500,000 kg/cm.sup.2) and a reduced difference between saturated shrinkage factors in lengthwise and widthwise directions which is prepared by stretching lengthwise 3.0 to 3.5 times and widthwise 3.3 to 3.8 times, and then similarly stretched widthwise and then subjecting to heat setting.
However, although such film of poly(ethylene-2,6-naphthalate) shows an enhanced dimensional stability, the film is satisfactorily improved in the curling tendency and reduction of strength. Further, in the case that the photographic Layer is formed on the film (support), the layer is not satisfactorily bonded to the surface of the film.